Multilayered tube and medical supply comprising multilayered tube

ABSTRACT

A multi-layered tube composed of at least two layers, each formed from a different resin, e.g. resin (I) or resin (II). Resin (I) contains 5 to 40 mass % of a polypropylene resin and 95 to 60 mass % of at least one hydrogenated copolymer. Resin (II) contains 45 to 100 mass % of a polypropylene resin and 55 to 0 mass % of a hydrogenated copolymer. The multi-layered tubes may be used in the field of medicine and provide tubing which is excellent in transparency, flexibility and anti-kinking properties, and which is durable during sterilization procedures with high-pressure steam. The multilayer tubing may also be safely disposed of as it generates no toxic gases, such as dioxin, when incinerated. The multilayered tubing has excellent connectability and may be bonded to other tubing using hot solvent bonding or solvent adhesion. The multilayered tubing which is free from generation of any toxic gas when incinerated, and which is excellent in hot solvent bonding or solvent adhesion to other tube.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a national-stage filing under 35 U.S.C. §371 ofPCT/JP00/06493, filed Sep. 22, 2000. This application also claimspriority under 35, U.S.C. §119 to Japanese application 2000-120270,filed Apr. 21, 2000.

TECHNICAL FIELD

The present invention relates to a multi-layered tube and a medicaldevice comprising the multi-layered tube. More specifically, the presentinvention relates to a multi-layered tube for medical use which isexcellent in flexibility, transparency, anti-kinking properties andrestoration capability after occlusion, which also has durabilityagainst high-pressure steam sterilization, and which is excellent inconnectability to other tube having a different diameter, a connecter, ajoint, and the like.

The multi-layered tube of the present invention is suitable for use as acomponent for medical devices such as a blood circuit line, a blood bag,a medicinal fluid bag, a blood transfusion/infusion set, a catheter, andthe like.

TECHNICAL BACKGROUND

Polyvinyl chloride has been and is widely used not only in the fields ofindustries and household articles but also in the fields of medicaltreatment and welfare. Particularly, most of disposable medical devicesare produced from polyvinyl chloride. Since, however, soft polyvinylchloride contains a relatively large amount of plasticizers such asdioctyl phthalate (DOP), etc., the problem of elution of the plasticizerinto blood or a medicinal solution is pointed out from the viewpoint ofsafety of medical devices.

On the other hand, from the viewpoint of infection prevention, steps aretaken forward to dispose medical devices, and it is required by the lawto dispose of used medical devices by incineration. It is said thatpolyvinyl chloride generates almost no toxic chlorine-containingsubstances such as dioxin since it is converted finally to carbondioxide, water and hydrogen chloride when combusted at a temperature ofapproximately 850 to 900° C. with feeding sufficient oxygen. In reality,however, the problem of environmental pollution with dioxin or othertoxic chlorine-containing substance frequently takes place for reasonsthat there are not sufficient incinerators that can withstand said hightemperatures, that there are small-sized incinerators of which theincineration capacity is insufficient and that there are few plants fordioxin disposal.

Studies are recently being made for changing the material in the fieldsof medical devices, industries and a household devices from the softvinyl chloride to other materials.

As a polyvinyl-chloride-free material for medical tubes, studies aremade on polyethylene (PE), polypropylene (PP), an ethylene-vinyl acetatecopolymer (EVAC), polyethyl methacrylate (PEMA), a styrene-butadieneblock copolymer, a hydrogenation product of a styrene-isoprene copolymer(styrene-based thermoplastic elastomer), and the like.

For example, as a resin composition that gives a molded articleexcellent in flexibility and suitable for medical use, JP-A-4-158868(Literature 1), JP-A-4-159344 (Literature 2) and JP-A-8-131537(Literature 3) propose a resin composition (styrene-based thermoplasticelastomer) containing an olefin resin, a hydrogenation product of astyrene-butadiene block copolymer (styrene-based thermoplasticelastomer) and a hydrogenation product of a styrene-isoprene blockcopolymer.

Further, JP-A-9-103493 (Literature 4) and JP-A-123314 (Literature 5)disclose a multi-layered tube formed of a substrate layer and anadhesive layer in which the adhesive layer is made of a material that isnot dimensionally stable at an autoclave sterilization temperature (121°C.) or higher and tends to flow under a connection pressure with othertube having a different diameter during autoclave sterilization at 121°C.

(1) In principle, however, a tube made of the above PE, EVAC or PEMA hasflexibility but has a problem that the tube, when made of a singlematerial, is liable to undergo kinking (which refers to a phenomenonthat the tube bends or is twisted to come into the state where internalsurfaces of the tube become stuck or adhered together).

(2) While the above styrene-based thermoplastic elastomer as a singlematerial or a composition containing 60 mass % thereof or more hasflexibility, they come to have sticking nature on the surface whensterilized with high-pressure steam (autoclave sterilization), so thatthey are not suitable for use as a material to form a surface that willcontact blood. Further, they have a problem that the internal surface ofthe tube undergoes self-sticking (self-adhesion) when the tube isclamped with a forceps and the tube shows poor restoration capabilitywhen it was released from clamping after occlusion.

(3) Further, a tube made of the above PP as a single material or acomposition containing at least 40 mass % thereof is too rigid and notflexible enough to prevent 1=4 kinking.

The resin composition described in the above Literatures 1 to 3 hascharacteristic features that it gives a molded article excellent inflexibility and it does not involve the generation of an toxic gas suchas dioxin when the molded article is incinerated. However, {circlearound (1)} when emphasis is placed on flexibility, a single-layeredtube made of the above resin composition has a higher proportion of thestyrene-based thermoplastic elastomer, and the tube suffers problemsthat are not negligible, that is, it has poor heat resistance problemthat the cross section of the tube sterilized in an autoclave isdeformed or one tube is fused with another or a problem that the tubehas poor restoration capability when released from clamping with aforceps after occlusion with it. {circle around (2)} When emphasis isplaced on heat resistance and restoration capability after occlusion,the proportion of the styrene-based thermoplastic elastomer comes to besmaller, and the tube becomes less flexible and is not at allsatisfactory as a medical tube. It is therefore desired to improve thetube in these points.

In a multi-layered tube, hot melt bonding or solvent bonding is the mostpreferred in view of reliable connection. In the multi-layered tubedescribed in Literature 4 or 5, the adhesive layer is made of a materialthat is not dimensionally stable at an autoclave sterilizationtemperature (121° C.) or higher and tends to flow under a connectionpressure with other tube having a different diameter during autoclavesterilization at 121° C., and the tube is connected to the other tube by“press fitting” between these tubes. These tubes are thereforeintimately connected by adherence, so that one tube easily comes offfrom the other under small force. Further, since tackiness is causedunder heat by the autoclave sterilization, fitted portions may comeapart one from the other during the sterilization or at a step priorthereto, and it is considered that such a material is not suitable forproducing medical devices.

As performances required for medical tube that can be sterilized withhigh-pressure steam, preferably, the tube satisfies the followingconditions:

That is, (a) the tube is to have proper flexibility without keeping onkinking or bending when bent, (b) the tube is to show no stickiness(tackiness) on the surface and is to be free from any change in form anddimensions when sterilized with high-pressure steam, and (c) the tubepermits hot melt bonding or solvent bonding when connected to other tubehaving a different diameter or an injection-molded article.

As described above, it is an object of the present invention to providea multi-layered tube which is excellent in transparency, flexibility,anti-kinking properties, restoration capability after occlusion and heatresistance and which elutes no plasticizer and generates no toxic gaswhen incinerated, and to provide a medical device comprising saidmulti-layered tube.

DISCLOSURE OF THE INVENTION

The present inventors have made diligent studies from the aboveviewpoints and as a result have found that the above object can beachieved by providing a multi-layered tube having layers havingdifferent compositions comprising a polypropylene resin and at least onecopolymer selected from a hydrogenated block copolymer of a polymerblock from a vinyl aromatic compound and an isoprene and/or butadieneblock and a hydrogenation product of a copolymer from a vinyl aromaticcompound and butadiene, and a medical device comprising the abovemulti-layered tube. The present invention has been accordingly made.

That is, according to the present invention, there are provided thefollowing inventions [1] and [2]. [1] A multi-layered tube composed ofat least two layers, wherein at least one layer of said layers is alayer (I) made of a resin composition comprising 5 to 40 mass % of apolypropylene resin (a),

and 95 to 60 mass % of at least one copolymer (b) selected from thegroup consisting of

-   -   a hydrogenated block copolymer (b1) obtained by hydrogenation of        a block copolymer formed of a polymer block (A) from a vinyl        aromatic compound and an isoprene polymer block (B),    -   a hydrogenated block copolymer (b2) obtained by hydrogenating a        block copolymer formed of a polymer block (A) from a vinyl        aromatic compound and a polymer block (C) from isoprene and        butadiene,    -   a hydrogenated block copolymer (b3) obtained by hydrogenating a        block copolymer formed of a polymer block (A) from a vinyl        aromatic compound and a butadiene polymer block (D), and    -   a hydrogenated copolymer (b4) obtained by hydrogenating a        copolymer of a vinyl aromatic compound and butadiene, and    -   at least one layer of the remaining layer or layers is a        layer (II) formed of a resin composition comprising 45 to 100        mass % of a polypropylene resin (a) and 55 to 0 mass % of the        above copolymer (b), and    -   further wherein said layer (I) forms one layer of an inner layer        and an outer layer and said layer (II) forms the other layer, or        said layer (I) forms an intermediate layer and the layer (II)        forms the inner layer and the outer layer.

[2] A medical device comprising said multi-layered tube and other memberto which said multi-layered tube is connected.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1A–1C shows cross-sectional views of multi-layered tubes 1 of thepresent invention.

FIG. 2 is a partially enlarged longitudinal sectional view of a medicaldevice comprising the multi-layered tube of the present inventionconnected to other connection member having a different diameter.

FIG. 3 is a partially enlarged longitudinal sectional view of a medicaldevice comprising the multi-layered tube of the present inventionconnected to other connection member having a different diameter.

In the drawings, 1 indicates a multi-layered tube, 3 indicates an innerlayer, 5 indicates an outer layer, 7 indicates an intermediate layer, 50indicates a connection member, 55 indicates an internal surface of theconnection member, 57 indicates an external surface of the connectionmember, I indicates a layer (I), and II indicates a layer (II).

PREFERRED EMBODIMENTS OF THE INVENTION

The present invention will be explained in detail hereinafter.

The polypropylene resin (a) for constituting the multi-layered tube ofthe present invention can be selected from known polypropylene resins,and it may be any one of homo polypropylene, random polypropylene andblock polypropylene. The polypropylene resins (a) may be used alone orin combination. Basically, when measured according to ASTMD-1238 at 230°C. under a load of 2,160 g, the polypropylene resin (a) preferably has amelt flow rate (MFR) in the range of from 0.1 to 500, more preferably inthe range of from 0.1 to 200.

As a polypropylene resin for the layer (I), the above polypropylenepreferably has a bending flexural modulus of 200 to 400 MPa(crystallinity of 30 to 40% and a molecular weight of 50,000 to200,000). As a polypropylene resin for the layer (II), the abovepolypropylene preferably has a bending flexural modulus of 500 to 900MPa (crystallinity of at least 50% and a molecular weight of 100,000 to500,000).

In principle, the layer (I) is a layer that forms a componentconstituting a substrate of the multi-layered tube, and the layer (II)is a layer that works as a connection layer when the multi-layered tubeis connected to other part to form a medical device.

When the polypropylene resin to be incorporated into the layer (I) has abending flexural modulus in the above range, the tube can be impartedwith flexibility and anti-kinking properties. When the flexural modulusis less than 200 MPa, the tube is too soft and exhibits no nerve(stiffness). When it exceeds 400 MPa, undesirably, the tube is liable tokeep on kinking and bending when bent.

When the polypropylene resin to be incorporated into the layer (II) hasa bending flexural modulus in the above range, the layer (II) can beimparted with a nerve (stiffness) so that flowing of the layer (II)during sterilization with high-pressure steam can be prevented.

The copolymer (b) used in the present invention is a hydrogenating blockcopolymer ((b1)–(b3)) obtained by hydrogenating a copolymer formed of apolymer block (A) from a vinyl aromatic compound and a polymer block((B)–(D)) from an isoprene and/or butadiene, or a hydrogenated copolymer(b4) obtained by hydrogenating a copolymer of a vinyl aromatic compoundand butadiene.

In the hydrogenated block copolymers ((b1)–(b3)), the vinyl aromaticcompound is preferably styrene, and the hydrogenated block copolymers((b1)–(b3)) are desirably a hydrogenated product (b1) of astyrene-isoprene-styrene copolymer, a hydrogenated product (b2) of astyrene-isoprene/butadiene-styrene copolymer, a hydrogenated product(b3) of a styrene-butadiene-styrene copolymer, and the like.

The hydrogenated copolymer (b4) is a hydrogenated copolymer obtained byhydrogenating a copolymer of a vinyl aromatic compound and butadiene asdescribed above. Preferably, the vinyl aromatic compound is styrene, andthe hydrogenated copolymer (b4) is a hydrogenatedstyrene-butadiene-rubber. It is particularly desirable to use a type ofthe hydrogenated copolymer (b4) that is ultra-finely dispersible inpolypropylene.

As a vinyl aromatic compound for the copolymer (b), such vinyl aromaticcompounds as described later can be used besides the styrene.

In the present invention, the layer (I) is a layer formed of a resincomposition containing 5 to 40 mass %, preferably 15 to 35 mass %, morepreferably 20 to 30 mass % of the polypropylene resin (a) and 95 to 60mass %, preferably 85 to 65 mass %, more preferably 80 to 70 mass % ofthe copolymer (b).

Basically, the multi-layered tube of the present invention has the layer(I) as a substrate layer, so that the multi-layered tube can be impartedwith flexibility and anti-kinking properties. That is, when the contentof the copolymer (b) exceeds 95 mass %, the tube is too soft and has nonerve, and when the tube is closed with a medical tube forceps for 15hours and then released from the forceps, the tube does not easily gaina through passage inside the tube within 3 seconds. Further, when thetube is subjected to heat-treatment such as autoclave sterilization(121° C., 20 minutes), the cross section of the tube is easily deformed.The tube is therefore poor in restoration capability after occlusion andheat resistance. Further, when the above content is less than 60 mass %,the resin composition has a high elastic modulus, and the tube has lowflexibility, so that the tube is undesirably liable to keep on kinkingor bending when bent.

Further, in the present invention, basically, the layer (II) to form aconnection layer is a layer formed of a a resin composition containing45 to 100 mass % of the polypropylene resin (a) and 55 to 0 mass % ofthe copolymer (b).

The composition for the layer (II) can be determined to be optimumdepending upon the object. That is, when the layer (II) is used as anouter layer, the content of the polypropylene resin (a) is at least 45mass %. In this case, sticking of one tube to another duringsterilization with high-pressure steam or sticking of the tube to apacking material can be prevented. When the multi-layered tube of thepresent invention is to be connected to other tube having a differentdiameter or to a part such as an injection-molded article with a solventbonding or an adhesive bonding or by hot melt bonding, preferably, thecontent of the polypropylene resin (a) in the layer (II) to constitutean connection layer (outer layer and/or inner layer) is determined to be70 mass % or less in view of adhesion capability.

When the layer (II) is used as an inner layer, the content of thepolypropylene resin (a) is determined to be at least 70 mass %. In thiscase, when the medical forceps is removed after the tube is closed withthe forceps, the tube can restore its original form in a short period oftime, and that the passage for a fluid can be secured. Further, when themulti-layered tube of the present invention is used in a way where it isbeing contact with blood like in a blood circuit or a blood tube,preferably, the content of the polypropylene resin (a) in the layer (II)that comes to be in contact with blood is at least 70 mass %, from theviewpoint of affinity to blood such as anti-coagulation of blood. As c)described above, the optimum composition for the layer (II) can bedetermined as required depending upon use.

In the present invention, the copolymer (b) is preferably the followinghydrogenated block copolymer ((b1)–(b3)) or a hydrogenated polymer (b4).

In the copolymer (b), the content of the vinyl aromatic compound ispreferably 10 to 40 mass %. When the content of the vinyl aromaticcompound is less than 10 mass %, the tube sometimes has insufficientmechanical strength. When it exceeds 40 mass %, the composition has ahigh melt viscosity, so that the vinyl aromatic compound is poorly mixedwith the polypropylene resin (a), which may impose limitations onmolding.

In the isoprene polymer block (B) of the hydrogenated block copolymer(b1), preferably, the content of 1,2-bonds and 3,4-bonds (to besometimes referred to as “vinyl bond content” hereinafter) is 10 to 75mass %. When the vinyl bond content is too small, such a content isinsufficient for transparency. When it is too large, the glasstransition temperature of the resin composition comes to be too high,and the flexibility of a molded article from the resin composition isliable to be impaired. When the hydrogenation ratio of carbon—carbondouble bonds in the copolymer (b1) is too small, the multi-layered tubetends to be poor in weatherability and heat resistance, so that theabove hydrogenation ratio is preferably at least 70%. The reference totransparency is made above, since when the multi-layered tube of thepresent invention is used as a component of a medical device, it isdesirable that the multi-layered tube has excellent transparency.

As the hydrogenated block copolymer (b2), it is preferred for the samereasons to use a hydrogenated block copolymer having anisoprene-butadiene copolymer block (C) having a 1,2-bond and 3,4-bondcontent of 20 to 85% and having carbon—carbon double bonds at least 70%of which are hydrogenated.

As the hydrogenated block copolymer (b3), it is also preferred for thesame reasons to use a hydrogenated block copolymer having a butadienepolymer block (D) having a 1,2-bond content of at least 30% and havingcarbon—carbon double bonds 70% of which are hydrogenated.

In the copolymer (b), examples of the vinyl aromatic compound includestyrene, α-methylstyrene, 1-vinylnaphthalene, 3-methylstyrene,4-propylstyrene, 4-cyclohexylstyrene, 4-dodecylstyrene,2-ethyl-4-benzylstyrene and 4-(phenylbutyl) styrene. Of these, styreneis particularly preferred.

Although not specially limited, the number average molecular weight ofthe polymer block (A) formed from the above vinyl aromatic compound ispreferably in the range of from 2,500 to 20,000.

Although not specially limited, the number average molecular weight ofeach of the polymer blocks (B), (C) and (D) is preferably in the rangeof from 10,000 to 200,000. While the form of a polymer from isoprene andbutadiene in the polymer block (C) is not specially limited, it may beany form of random, block and tapered forms.

In the copolymer (b), the form of bonding of each polymer block ((B),(C) or (D)) is not specially limited, and it may be linear, branched orany combination of these. Specific examples of the molecular structureof the copolymer (b) include P(QP)_(n) and (PQ)_(n), in which P is thepolymer block (A), Q is a polymer block (B), (C) or (D) and n is aninteger of 1 or greater.

As the copolymer (b), further, there can be used a copolymer having astar-shaped molecular structure obtained in the presence ofdivinylbenzene, a tin compound or a silane compound as a coupling agent(e.g., a polymer represented by [(PQ)_(m)X] in which P and Q are asdefined above, m is an integer of 2 or greater and X is a residue of thecoupling agent.

As the copolymer (b), copolymers having the above various molecularstructures may be used alone, or two or more copolymers having the abovevarious molecular structures such as a mixture of triblock type anddiblock type copolymers may be used. The number average molecular weightof the above copolymer (b) is preferably in the range of from 30,000 to300,000.

The method for producing the copolymer (b) can be selected from knownproduction methods, and for example, there can be employed a method ofhydrogenating a block copolymer obtained by any one of the followingmethods (α) to (γ), that is,

-   -   (α) a method in which a vinyl aromatic compound is polymerized        in the presence of an alkyllithium compound as an initiator, and        then a conjugated diene compound (isoprene, butadiene) and a        vinyl aromatic compound are consecutively polymerized,    -   (β) a method in which a vinyl aromatic compound is polymerized,        then a conjugated diene compound is polymerized, and the        coupling of the resultant block copolymers is carried out in the        presence of a coupling agent, and    -   (γ) a method in which a conjugated diene compound is polymerized        in the presence of a dilithium compound as an initiator and then        a vinyl aromatic compound is consecutively polymerized.

In the above method, the alkyllithium compound as an initiator isselected from compounds whose alkyl group has 1 to 10 carbon atoms, andof these, methyllithium, ethyllithium, pentyllithium, n-butyllithium,s-butyllithium and t-butyllithium are preferred. Examples of thecoupling agent for coupling the block copolymer include halogencompounds such as dichloromethane, dibromomethane, dichloroethane,dibromoethane, dibromobenzene and tin tetrachloride; ester compoundssuch as phenyl benzoate and ethyl acetate; divinylbenzene, and varioussilane compounds. Further, examples of the dilithium compound as aninitiator include naphthalenedilithium and dilithiohexylbenzene.

The amount of the above initiator or the coupling agent is determined asrequired depending upon the molecular weight of a desired blockcopolymer. Per 100 parts by weight of all the entire monomers used forthe polymerization, generally, the amount of the initiator is in therange of from 0.01 to 0.2 part by weight, and the amount of the couplingagent is in the range of from 0.04 to 0.8 part by weight.

The vinyl bond content in each of the polymer blocks N (B) to (D) can becontrolled by the use of a Lewis base as a cocatalyst in thepolymerization. Examples of the above Lewis base include ethers such asdimethyl ether, diethyl ether and tetrahydrofuran; glycol ethers such asethylene glycol dimethyl ether and diethylene glycol dimethyl ether; andamine-containing compounds such as triethylamine,N,N,N′,N′-tetramethylethylenediamine (to be abbreviated as “TMDA”hereinafter) and N-methylmorpholine. The Lewis base is used in such anamount that the molar amount of the Lewis base per mole of the lithiumatom in the polymerization initiator is in the range of from 0.1 to1,000 mol.

In the polymerization, it is preferred to use an organic solvent inertto the polymerization initiator as a solvent. The above solvent ispreferably selected from aliphatic hydrocarbons having 6 to 12 carbonatoms such as hexane and heptane; alicyclic hydrocarbons such ascyclohexane and methylcyclohexane; or aromatic hydrocarbons such asbenzene. In any one of the above polymerization methods (α) to (γ), thepolymerization is generally carried out at a temperature range of from 0to 80° C., and the reaction time period is generally 0.5 to 50 hours.

Then, the block copolymer obtained by the above method is converted tothe hydrogenated block copolymer (b1), (b2) or (b3), for example, by aknown method, such as a method in which hydrogen in a molecular state isreacted with the block copolymer in the presence of a knownhydrogenation catalyst in a state where the block copolymer is dissolvedin a solvent inert to the reaction. The above hydrogenation catalyst isselected from heterogeneous catalysts composed of a metal such as Raneynickel, Pt, Pd, Ru, Rh or Ni supported on a carrier such as carbon,alumina or diatomaceous earth to support; Ziegler catalysts formed ofcombinations of organometalic compounds of metals belonging to the groupVIII of the periodic table such as nickel and cobalt with organicaluminum compounds or organic lithium compounds such as triethylaluminumand triisobutylaluminum; or metallocene catalysts formed of combinationsof bis(cyclopentadienyl) in compounds of transition metals such astitanium, zirconium and hafnium with an organometalic compound oflithium, sodium, potassium, aluminum, zinc or magnesium.

The hydrogenation is generally carried out under a hydrogen pressure inthe range of from normal pressure to 20 MPa at a reaction temperature inthe range of from room temperature to 250° C. The reaction time periodis generally 0.1 to 100 hours. The copolymer (b) obtained by the abovehydrogenation is recovered (i) by coagulating the reaction mixture inmethanol, or the like and then heating the coagulated reaction mixtureor drying it under reduced pressure, or (ii) by carrying out so calledsteam stripping in which the reaction solution is poured into boilingwater and the solvent is azeotropically removed, and heating thereaction product or drying it under reduced pressure.

In the multi-layered tube of the present invention, the layer (I)preferably has an elastic modulus (elastic modulus of the layer per se)of 30 MPa or less at 25° C. Further, each of the layer (I) and the layer(II) preferably has a haze of 25% or less at the thickness of 1 mm.Further, preferably, the multi-layered tube of the present invention canform an arc having a radius of 20 mm without kinking.

The multi-layered tube of the present invention may be used as it is.Practically and preferably, however, the layer(s) (II) forming the outersurface and/or the inner surface of the multi-layered tube is/are usedas connection layer(s), and other tube having a different diameter, aconnector or a joint is connected thereto before use. The aboveconnection is attained by solvent bonding or hot melt bonding, or may beattained by bonding with an adhesive.

Further, in the multi-layered tube of the present invention, preferably,the shear peel strength of the stuck portion (adhered portion) ofoutermost layers of the multi-layered tubes after autoclavesterilization at 121° C. for 20 minutes is 35 N or lower, and the 180°peel strength of an stuck portion of the outermost layer and apolyolefin such as polypropylene forming the innermost layer after thesterilization is 5 N or lower. The term “180° peel strength” in thepresent invention refers to a strength measured by a test method definedin JIS K6854.

The multi-layered tube of the present invention is suitable as a medicaltube for an extracorporeal circulation circuit, and, preferably, themulti-layered tube can form a through passage inside it within 3 secondswhen it is closed with a medical tube forceps for 15 hours and thenreleased from the forceps.

Each resin composition for constituting the multi-layered tube of thepresent invention may contain additives such as an antioxidant, an UVabsorbent, a light stabilizer, a colorant, a crystal nucleating agent,etc., in such amounts that the properties of the multi-layered tube arenot impaired. Generally, the amount of these additives per 100 parts bymass are in the range of from 0.01 to 5 part by mass.

Each resin composition for constituting the multi-layered tube maycontain other polymers such as hydrogenated polyisoprene, hydrogenatedpolybutadiene, a hydrogenated styrene-isoprene random copolymer, butylrubber, polyisobytylene, polybutene, ethylene-propylene rubber, anethylene-α-olefin copolymer, an ethylene-vinyl acetate copolymer, anethylene-methacrylic acid copolymer, an ethylene-acrylic acid coplymer,ionomers of these, an ethylene-ethyl acrylate copolymer, anethylene-methyl methacrylate copolymer, an ethylene-ethyl methacrylatecopolymer, atactic polypropylene, and the like, in such amounts that thegist of the present invention is not impaired. The above resincompositions may be crosslinked by a general crosslinking method using aperoxide, etc., before use.

The resin compositions for constituting the multi-layered tube of thepresent invention may be prepared by kneading the polypropylene resin(a), the copolymer (b) and optionally the above additive(s) with akneading machine such as a single-screw extruder, a twin-screw extruder,a kneader, a Banbury mixer, a roll, or the like. The thus-prepared resincompositions are formed into the multi-layered tube by co-extrusion orcoating.

The multi-layered tube of the present invention is excellent inflexibility, transparency, anti-kinking properties, restorationcapability after occlusion and heat resistance. That is, specifically,{circle around (1)} when an optical bubble detector is used, 1 mL singlebubble is detected at a flow rate of 300 mL/minute, 2 each of thecompositions forming the layers has a haze of 25% or less at thethickness of 1 mm, {circle around (3)} when the multi-layered tube isformed into an arc having a radius of 20 mm, it is not bent, {circlearound (4)} when the multi-layered tube is closed with a medical tubeforceps for 15 hours and then released from the forceps, the tube formsa through passage inside within 3 seconds, and {circle around (5)} afterthe multi-layered tube is sterilized in an autoclave (121° C., 20minutes), the shear peel strength of the stuck portion of the outermostlayers of the multi-layered tubes is 35 N or lower, and the 180° peelstrength of an stuck portion of the outermost layer of the tube and asterilization bag having the innermost layer formed of polypropylene is5 N or lower.

One example of the embodiment of the present invention will be explainedwith reference to attached drawings hereinafter. FIG. 1A–1C showscross-sectional views of multi-layered tubes of the present invention.FIGS. 2 and 3 are partially enlarged longitudinal sectional views ofmedical device comprising the multi-layered tube of the presentinvention connected to other connection members such as other tubehaving a different diameter and an injection-molded article. Inaddition, the injection-molded article in the present invention refersto a tubular member connectable to the multi-layered tube of the presentinvention and includes, for example, a connector and a joint.

In FIG. 1A, a multi-layered tube 1 is a dual layered tube formed of thelayer (I) forming an inner layer 3 and the layer (II) forming an outerlayer 5. In FIG. 1B, a multi-layered tube 1 is a dual layered tubeformed of the layer (I) forming an outer layer 5 and the layer (II)forming an inner layer 3. In FIG. 1C, further, a multi-layered tube 1 isa three-layered tube formed of the layer (I) forming an intermediatelayer 7 and the layers (II) forming an inner layer 3 and an outer layer5.

FIG. 2 shows a state in which the dual layered tube 1 shown in FIG. 1Ais connected to a connection member 50 such as other tube having adifferent diameter or an injection-molded article, and the layer (II)forming the outer layer 5 and an inner wall surface 55 of the connectionmember 50 can be connected to each other. The term “connection” meansconnection with a solvent bonding or hot melt bonding as alreadydescribed. The adhesion by hot melt bonding includes application of ahot melt bonding using electric heat, high-frequency hot melt bondingand hot melt bonding by heating with hot air. However, the bonding shallnot be limited thereto, and other hot melt bonding may be employed. FIG.3 also shows a state where the dual tube shown in FIG. 1B and theconnection member 50 are connected to each other, and the layer (II)forming the inner layer 3 and an outer wall surface 57 of the connectionmember 50 are connected to each other similarly with a solvent bondingor by hot melt bonding.

In the dual layered tube, the thickness ratio of the layer (I) and thelayer (II), layer (I)/layer (II), is preferably 940–980/60–20. That isbecause the entire tube is imparted with flexibility and anti-kinkingproperties by allowing the layer (I) to have a sufficient thickness ascompared with the layer (II). That is, when the thickness ratio of thelayer (I) is less than 940 (when the thickness ratio of the layer (II)exceeds 60), the wall thickness of the tube is small and kinking isliable to occur. When the thickness ratio of the layer (I) exceeds 980(when the thickness ratio of the layer (II) is less than 20), the tubewall thickness is extremely large, and the rigidity is too large, sothat the tube is liable to have decreased flexibility. Further, thethickness of the layer (II) is too small, and the tube tends to be nolonger suitable for application of solvent bonding or hot melt bonding.

In the three-layered tube, the thickness ratio of the layer (I) and thelayers (II), layer (II)/layer (I)/layer (II), is preferably20–30/940–960/20–30. When the thickness ratio of the layer (I) is lessthan 940 (when the thickness ratio of the layer(s) (II) exceeds 30), thetube wall thickness is too small, and kinking is liable to occur. Whenthe thickness ratio of the layer(s) (II) is less than 20 (when thethickness ratio of the layer (I) exceeds 960), the thickness of thelayer (II) is too small, so that it is difficult to apply solventbonding or hot melt bonding.

When the multi-layered tube of the present invention as a component isconnected to a member such as other tube having a different diameter oran injection-molded article as described above, it can suitably formmedical devices such as a blood circuit, a blood bag, a catheter, or thelike.

The multi-layered tube of the present invention makes the best use ofthe above properties and can be used in an extracorporeal circulationcircuit such as a blood circuit for artificial kidney dialysis, a bloodcircuit for blood plasma exchange, a circuit for ascites treatmentsystems by filtration, concentration and infusion, or the like. Further,in addition to the above extracorporeal circulation circuit, themulti-layered tube of the present invention can be used, for example, invarious medical devices such as a blood tube, an infusion tube, acatheter, a balloon catheter, etc., industrial uses such as a hose,fields in agricultures, forestry and fisheries and the field ofhousehold articles, where excellent flexibility and transparency arerequired.

EXAMPLES

The present invention will be explained with reference to Exampleshereinafter, in which “%” stands for “mass %” unless otherwisespecified.

In the following Referential Examples 1 and 2, Examples 1 to 5 andComparative Example 1, multi-layered tubes were evaluated for stickingof tubes to each other during sterilization, anti-kinking properties andadhesion by the following methods.

(Sticking During Sterilization)

Tubes were fixed with a paper tape so as to intimately adhere to eachother, and the tubes were sterilized in an autoclave at 121° C. for 20minutes and then measured for a shear peel resistance.

(Kinking Occurrence Radius)

Both ends of a 20 cm long tube were fixed to tools, the distance betweenthe tools was gradually decreased, dimensions were taken when the tubewas bent, and a radius of curvature was calculated.

(Solvent Bonding Properties)

A tube that had an internal diameter of 6.8 mm and was prepared from thesame composition as that of an adhesive layer was used for bonding withTHF, and after 24 hours, the tube was measured for a tensile strength.

Referential Example 1 Determination of Amount Ratio for Layer (II)

For the layer (II), polypropylene (F327) and a styrene-isoprene-styrenehydrogenated block copolymer (HVS-3) were mixed in amount ratios shownin Table 1 to prepare a tube having an outer diameter of 6.8 mm, and thetube was measured for sticking strength during sterilization andstrength of solvent bonding. Table 1 shows the results.

TABLE 1 Sticking strength Strength of bonding Amount ratio of PP of onetube to tube having a (a)/Copolymer (b) to another different diameter100/0  No sticking  6 N 70/30 Less than 10 N 90 N 50/50 34 N 97 N 40/6036 N 105 N 

According to the results in Table 1, when the amount ratio of thepolypropylene resin (a), in the amount ratio of the polypropylene resin(a) and the copolymer (b), is 70 or less (when the amount ratio of thecopolymer (b) is 30 or greater), the bonding strength of the tube to thetube having a different diameter is good. However, when the amount ratioof the polypropylene resin (a) is 40 or less (when the amount ratio ofthe copolymer (b) is 60 or greater), undesirably, the sticking strengthof the tubes to each other comes to be 36 N or more.

When the amount ratio of the polypropylene resin (a) exceeds 70 (whenthe amount ratio of the copolymer (b) is less than 30), the sticking ofthe tubes to each other is desirably less than 10 N. Undesirably,however, the bonding strength to the tube having a different diameter isless than 90 N.

It is therefore seen that the polypropylene resin (a)/copolymer (b)amount ratio is preferably determined to be 70/30 to 45/55 forpreventing the sticking of tubes to one another during sterilization andmaintaining the strength of solvent bonding to a tube having a differentdiameter.

Examples 1–5 and Comparative Example 1

A commercially available polypropylene [F327 (trade name), supplied byGrand Polymer Inc., flexural modulus (JIS K7203): 780 MPa] was used as apolypropylene resin (a), and a commercially available hydrogenatedstyrene-ethylene-butylene-styrene block copolymer [Kraton G G1652 (tradename), supplied by Shell Chemical Co.], a hydrogenated isoprenecopolymer [Hybrar HVS-3 (trade name), supplied by Kuraray Ltd.] or ahydrogenated styrene-butadiene rubber [DYNARON 1320P (trade name),supplied by JSR] was used as a copolymer (b).

The above polypropylene resin (a) and the copolymer (b) were mixed in amixing ratio shown in Table 2, to prepare a resin composition.

The above resin compositions were co-extruded to form a three-layeredtube having a layer (II) (outer layer)/layer (I) (intermediatelayer)/layer (II) (inner layer) structure.

The three-layered tube has a size of 7 mm as an outer diameter and 1 mmas a wall thickness, and the thickness ratio of the layer (I) and thelayers (II) were as shown in Table 2.

The above multi-layered tube was measured for stickiness of tubes toeach other during sterilization, anti-kinking properties and bondingproperties, and Table 2 shows the results.

As is clearly shown in Table 2, the three-layered tubes of Examples 1 to5 according to the present invention nearly satisfy the formerlydescribed performances (a) to (c) which a medical tube is required tohave. In contrast, when the amount ratio of the polypropylene isdecreased and the amount ratio of the copolymer (b) is increased in thecomposition for the layers (II) like Comparative Example 1, the stickingduring sterilization increases.

In Referential Examples 2 to 4, Examples 6 to 16 and ComparativeExamples 2 and 3, polymers were measured for styrene contents, numberaverage molecular weights, vinyl bond contents and hydrogenation ratios,molded articles from resin compositions were measured for flexibilityand transparency, and tubes were measured for transparency, anti-kinkingproperties, restoration capability after occlusion and heat resistance,by the following methods.

(Styrene Content)

Calculated on the basis of mass of each monomer used for polymerization.

(Number Average Molecular Weight)

A number average molecular weight (Mn) as polystyrene was determined byGPC measurement.

(Vinyl Bond Content)

A block copolymer before hydrogenation was dissolved in deuteratedchloroform (CDCl₃) and measured for ¹H-NMR spectrum, and a vinyl bondcontent was calculated on the basis of sizes of peaks corresponding to1,2-bonds and 3,4-bonds.

(Hydrogenation ratio)

Hydrogenation ratio was calculated on the measurement of iodine numbersof the block copolymer before and after hydrogenation.

TABLE 2 Example 1 Example 2 Example 3 Amount Layer (a) PP F327 (a) PPF327 (a) PP F327 ratio (I) 20% 20% 20% (%) (b) KratonGG1 (b) Hybrar (b)DYNARON 652 80% HVS-3 1320P 80% 80% Layer (a) PP F327 (a) PP F327 (a) PPF327 (II) 50% 50% 50% (b) KratonGG1 (b) Hybrar (b) DYNARON 652 50% HVS-31320P 50% 50% Thicknes Laver 940 940 940 ratio (I) Layer 30 × 2 30 × 230 × 2 (II) Sticking during 3~3.4 3~3.4 3~3.5 srerilization Radius when17 mm 17 mm 16 mm kinking occurred Solvent bonding 90~120 N 90~120 N90~110 N properties Comparative Example 4 Example 5 Example 1 AmountLayer (a) PP F327 (a) PP F327 (a) PP F327 ratio (I) 20% 20% 20% (%) (b)Hybrar (b) Kraton- (b) Hybrar HVS-3 80% GG1652 HVS-3 80% 80% Layer (c)PP F327 (a) PP F327 (a) PP F327 (II) 50% 100% 40% (d) Hybrar (b) HybrarHVS-3 50% HVS-3 60% Thicknes Layer 800 940 940 ratio (I) Layer 100 × 230 × 2 30 × 2 (II) Sticking during 3~3.4 No sticking 3.4~3.8sterilization Radius when 23 mm 37 mm 17 mm kinking occurred Solventbonding 90~110 N Less than 10 N 90~110 N properties(Flexibility of Resin Composition)

A test piece having a length of 30 mm, a width of 5 mm and a thicknessof 1 mm was prepared, and measured for a dynamic viscoelasticitydependent upon temperatures. The elastic modulus at 25° C. was employed.Measurement conditions were as follows. Tensile mode (sine wavedistortion, amplitude displacement; 10 μm, frequency; 1 Hz), achuck—chuck distance; 20 mm, measurement temperature range; −100–150°C., a temperature elevation rate; 3° C./minute

(Transparency of Resin Composition)

A sheet having a thickness of 1 mm was prepared, and measured for a hazevalue with a haze meter according to a method defined in JIS K7105, andthe haze value was used as an index for transparency of a resincomposition.

(Transparency of Tube)

When a tube was filled with water, a degree to which air bubbles insidethe tube were visually observed was used as an index for transparency.

(Anti-Kinking Properties of Tube)

A tube having a length of 20 cm was bent in the form of a U-letter andleft as it was for approximately 1 minute, and then the tube wasobserved for a kinking. The tube was measured for a radius of curvaturewith an R gage, and a smallest radius of curvature at which no kinkingoccurred was used as an index for anti-kinking properties.

(Restoration Capability of Tube after Occlusion)

A tube filled with a saline solution was closed with a medical tubeforceps for 15 hours, and then the forceps was removed. A time periodwas measured before the tube formed a through passage inside and used asan index for restoration capability of tube after occlusion.

(Resistance Against Tube/Tube Sticking Under Heat)

Two tubes having a length of 10 cm each were stacked such that 5 cm eachof them were stacked one on the other in parallel, and the stackedportions were bound with a paper tape. The tubes were subjected toautoclave sterilization (121° C., 20 minutes), and the binding papertape was removed. The tubes were measured for a shear peel strength, andthe tube/tube sticking strength was used as an index for resistanceagainst sticking under heat. As a shear peel strength, a maximum valueobtained under conditions of a test speed of 100 mm/minute with atensile tester was employed.

(Resistance Against Tube/Film Sticking Under Heat)

A tube having a length of 10 cm was placed in a sterilization bag(supplied by Hogy Medical Co.) and subjected to autoclave sterilization(121° C., 20 minutes). Then, the film was measured for a 180° peelstrength, and By the tube/film sticking was used as an index forresistance against sticking under heat. As a shear peel strength, anaverage value obtained under conditions of a test speed of 100 mm/minutewith a tensile tester was employed.

Referential Example 2 Preparation of Copolymer No. 1

In a pressure vessel where dry nitrogen had been substituted, styrenewas polymerized at 60° C. in cyclohexane as a solvent in the presence ofs-butyllithium as a polymerization initiator, and then TMEDA was addedas a Lewis base. Then, isoprene and styrene were consecutivelypolymerized to give a styrene-isoprene-styrene block copolymer. Thethus-obtained block copolymer was hydrogenated in cyclohexane in thepresence of Pd/C as a catalyst under a 2 MPa hydrogen atmosphere, togive a hydrogenated block copolymer (the hydrogenated block copolymerobtained in Referential Example 2 will be abbreviated as “Copolymer No.1” hereinafter). Table 3 shows a styrene content, a number averagemolecular weight, a vinyl bond content and a hydrogenation ratio of theobtained Copolymer No. 1.

Referential Example 3 Preparation of Copolymer No. 2

Styrene, a mixture of isoprene with butadiene [isoprene/butadiene=60/40(mass ratio)] and styrene were consecutively polymerized in acyclohexane solvent in the presence of s-butyllithium and TMEDA in thesame manner as in Referential Example 2, to give astyrene-(isoprene/butadiene)-styrene block copolymer. The thus-obtainedblock copolymer was hydrogenated in the same manner as in ReferentialExample 2, to give a hydrogenated block copolymer (the hydrogenatedblock copolymer obtained in Referential Example 3 will be abbreviated as“Copolymer No. 2” hereinafter). Table 3 shows a styrene content, anumber average molecular weight, a vinyl bond content and ahydrogenation ratio of the obtained Copolymer No. 2.

Referential Example 4 Preparation of Copolymer No. 3

Styrene, butadiene and styrene were consecutively polymerized in acyclohexane solvent in the presence of s-butyllithium and TMEDA in thesame manner as in Referential Example 2, to give astyrene-butadiene-styrene block copolymer. The thus-obtained blockcopolymer was hydrogenated in the same manner as in Referential Example2, to give a hydrogenated block Copolymer No. 3 (the hydrogenated blockcopolymer obtained in Referential Example 4 will be abbreviated as“Copolymer No. 3” hereinafter). Table 3 shows a styrene content, anumber average molecular weight, a vinyl bond content and ahydrogenation ratio of the obtained Copolymer No. 3.

TABLE 3 Molecular structure Number before average Vinyl Hydrogen- Co-hydrogen- Styrene molecular bond ation polymer ation content weightcontent ratio No. (Note) (%) (× 10⁴) (mol %) (%) REx. 2 1 A-B-A 20 10.355 80 REx. 3 2 A-C-A 20 10.8 60 82 REx. 4 3 A-D-A 20 10.5 72 83 (Note)A: Polystyrene block B: Polyisoprene block C: Poly(isoprene/butadiene)block D: Polybutadiene block

Examples 6–9 and Comparative Examples 2–3

As a polypropylene resin (a), a commercially available block typepolypropylene [BClB (trade name), supplied by Nippon Polychem.], arandom type polypropylene [J215W (trade name), supplied by Grand PolymerCo.] and a homo type polypropylene [MA3 (trade name), supplied by NipponPolychem.] were used. As a copolymer (b), Copolymer No. 1 obtained inReferential Example 2, Copolymer No. 2 obtained in Referential Example3, Copolymer No. 3 obtained in Referential Example 4 and a commerciallyavailable hydrogenated styrene-butadiene rubber [DYNARON 1320P (tradename), supplied by JSR Co., Ltd] were used.

The polypropylene resin (a) and the copolymer (b) were kneaded in anamount ratio (ratio by mass) shown in Table 4 at 230° C. in a twin-screwextruder, to give resin compositions.

TABLE 4 Example 6 Example 7 Examle 8 Layer (I) (a) PP BC1B (a) PP J215W(a) PP J215W (Thickness 1 mm) (5%) (40%) (20%) (b) Copolymer (b) Copoly-(b) Copolymer No. 1 (95%) mer No. 2 No. 3 (80%) (60%) Layer (II), inner(a) PP BC1B None None layer (Thickness, (90%) 30 μm) (b) Copolymer No. 1(10%) Layer (II), outer None (a) PP J215W (a) PP J215W layer (Thickness,(80%) (50%) 30 μm) (b) Copoly- (b) Copolymer mer No. 2 No. 3 (50%) (20%)Flexibility of ⊚ ∘ ⊚ tube*¹ Elastic modulus 8.5 MPa 50 MPa 11 MPa oflayer (I) Transparancy of ∘ ∘ ∘ tube*² Haze of layer (I)  2%  5% 4% (%)Haze of layer (II) 20% 16% 7% (%) Anti-kinking ∘ 12 mm ∘ 12 mm ∘ 11 mmproperties*³ Remarks None None None Comparative Comparataive Example 9example 2 example 3 Layer (I) (a) PP MA3 (a) PP BC1B (a) PP J215W(Thickness 1 mm) (30%) (3%) (50%) (b) DYNARON (b) Copoly- (b) Copolymer1320P (70%) mer No. 1 No. 2 (50%) (97%) Layer (II), inner None (a) PPBC1B None layer (Thickness (90%) 30 μm) (b) Copoly- mer No. 1 (10%)Layer (II), outer (a) PP MA3 None (a) PP J215W layer (Thickness (100%)(80%) 30 μm) (b) Copolymer No. 2 (20%) Flexibility of ⊚ ⊚ x tube*¹Elastic modulus 15 MPa 8 MPa 100 MPa of layer (I) Transparancy of ∘ ∘ ∘tube*² Haze of layer (I)  4%  1%  7% (%) Haze of layer (II) 25% 20% 16%(%) Anti-kinking ∘ 13 mm ∘ 12 mm ∘ 15 mm properties*³ Remarks None Crosssection deficient in of tube flexibility deformed to oval (Notes)*¹Evaluation of flexibility of tube was based on elastic modulus oflayer (I); ⊚: less than 30 MPa, ∘: 30–100 MPa, x: over 100 MPa*²Evaluation base of transparency of tube: ∘ Air bubbles wererecognizable, x: No air bubble was recognizable. *³Evaluation ofanti-kinking properties of tube was based on maximum diameter at whichkinking occurred; ∘: less than 20 mm, x: over 20 mm

The obtained resin compositions were formed at 230° C. into a dual layertube having an outer diameter of 5.6 mm and an inner diameter of 3.3 mm,and the dual tube was evaluated for flexibility, transparency,anti-kinking properties, resistance against sticking under heat andrestoration capability after occlusion. Table 4 shows the results.

It is seen from Table 4 that the multi-layered tubes of Examples 6 to 9are excellent in flexibility, transparency and anti-kinking properties,but that when the amount ratio of the polypropylene resin in the layer(I) is small like Comparative Example 2, it is difficult to form a tubeand the cross section of the tube is deformed. Further, when the a)amount ratio of the polypropylene resin in the layer (I) is large likeComparative Example 3, the flexibility of the tube is deficient.

Examples 10–13

A commercially available random type polypropylene [J215W (trade name),supplied by Grand Polymer Co.] was used as a polypropylene resin (a),and copolymer No. 1 obtained in Referential Example 2 was used as acopolymer (b).

The above polypropylene resin (a) and the copolymer (b) were kneaded inan amount ratio (ratio by mass) shown in Table 5 at 230° C. in atwin-screw extruder, to give a resin composition. The obtained resincompositions were formed at 230° C. into a three-layered tube having anouter diameter of 5.6 mm and an inner diameter of 3.3 mm as shown inFIG. 1(3), and the three-layered tube was evaluated for flexibility,transparency, anti-kinking properties, resistance against sticking underheat and restoration capability after occlusion. Table 5 shows theresults. It is seen from Table 5 that the multi-layered tubes inExamples 10 to 13 are excellent in flexibility, transparency,anti-kinking properties, resistance against sticking under heat andrestoration capability after occlusion.

Example 14

A dual layered tube having an outer diameter of 8 mm and an innerdiameter of 6 mm was prepared in the same manner as in Example 8, and athree-layered tube having an outer diameter of 6 mm and an innerdiameter of 4 mm was prepared in the same manner as in Example 10. Thesetubes were connected by solvent bonding using tetrahydrofuran. Thebonded portion had a tensile bonding strength of 130 N, or attainedstrong connection.

TABLE 5 Table 10 Table 11 Table 12 Table 13 Layer (I) (a) PP J215W (20%)(a) PP J215W (20%) (a) PP J215W (20%) (a) PP J215W (20%) (Thickness 1mm) (b) Copolymer No. 1 (b) Copolymer No. 1 (b) Copolymer No. 1 (b)Copolymer No. 1 (80%) (80%) (80%) (80%) Layer (II), inner layer (a) PPJ215W (60%) (a) PP J215W (60%) (a) PP J215W (40%) (a) PP J215W(Thickness 30 μm) (100%) (b) Copolymer No. 1 (b) Copolymer No. 1 (b)Copolymer No. 1 (40%) (40%) (60%) Layer (II′), outer layer (a) PP J215W(50%) (a) PP J215W (40%) (a) PP J215W (70%) (a) PP J215W (60%)(Thickness 30 μm) (b) Copolymer No. 1 (b) Copolymer No. 1 (b) CopolymerNo. 1 (b) Copolymer No. 1 (50%) (60%) (30%) (40%) Flexibility of tube*¹⊚ ⊚ ⊚ ⊚ Elastic modulfs of layer (I) 12 MPa 12 MPa 12 MPa 12 MPaTransparendy of tube*² ∘ ∘ ∘ ∘ Haze of layer (I) (%) 3% 3% 3%  3% Hazeof layer (II) (%) 11%  11%  5% 25% Haze of layer (II′) (%) 7% 5% 14% 11% Anti-kinking properties*³ ∘ 12 mm ∘ 11 mm ∘ 15 mm ∘ 13 mm Resistanceagainst sticking under heat*⁴ ⊚ ∘ ⊚ ⊚ Shear peel strength Tube/tube 34 N37 N 14 N 20 N 180° Peel strengh Tube/film  2 N 10 N  1 N  2 NRestoration capability after occlusion*⁵ ∘ 3 seconds ∘ 3 seconds ∘ 15seconds ⊚ 2 seconds Remauks None None None None (Notes) *¹Evaluation offlexibility of tube was based on elastic modulus of layer (I); ⊚: lessthan 30 MPa, ∘: 30–100 MPa, x: over 100 MPa *²Evaluation base oftransparency of tube: ∘ Air bubbles were recognizable, x: No air bubblewas recognizable. *³Evaluation of anti-kinking properties of tube wasbased on maximum diameter at which kinking occurred; ∘: less than 20 mm,x: 20 mm or more *⁴Evaluation of resistance against sticking under heatwas based on shear peel strength of tube/tube sticking; ⊚: less than 35N, ∘: 35–40 N, x: over 40 N and also based on 180° peel strength; ∘:less than 1.0 N, x: 10 N or more *⁵Evaluation of restoration capabilityafter occlusion was based on time period for which through passage wasformed; ⊚: less than 3 seconds, ∘: 3–120 seconds, x: over 120 seconds

Example 15

The three-layered tube prepared in Example 10 was used to obtain a bloodcircuit for dialysis. The three-layered tube was strongly connected to aconnector. A three-layered tube portion of the blood circuit was closedwith a medical tube forceps for 15 hours, and then the forceps wasremoved. The tube formed a through passage inside within 3 seconds afterthe removal. The above three-layered tube is excellent in flexibility,transparency, anti-kinking properties, restoration capability afterocclusion and resistance against sticking under heat, and it is shownthat it is at a practical level when it is used in a medical device or amedical tube, particularly, a circuit for extracorporeal circulation.

Comparative Example 4

A commercially available polypropylene [F327 (trade name), supplied byGrand Polymer Co.] was used as a polypropylene resin (a), Copolymer No.1 obtained in Referential Example 2 was used as a copolymer (b), andthese were used for a layer (I) (intermediate layer) and a layer (II) asan outer layer. A high-density polyethylene [HJ490 (trade name),supplied by Japan Polychem Co.] was used for a layer (II) as an innerlayer. And, a three-layered tube having a constitution shown in Table 6was prepared. When the three-layered tube was closed with a forceps for15 hours after sterilization with high-pressure steam, the time periodbefore the formation of a through passage was 120 seconds or longer.

TABLE 6 Comparative Example 4 Layer (I) (a) PP F327 (30%) (thickness 1mm) (b) copolymer No. 1 (70%) Layer (II), inner layer High-densitypolyethylene (thickness 30 μm) HJ490 Layer (II), outer layer (a) PP F327(50%) (thickness 30 μm) (b) copolymer No. 1 (50%)

INDUSTRIAL UTILITY

According to the present invention, there is provided a multi-layeredtube that is excellent in flexibility, transparency, anti-kinkingproperties, restoration capability after occlusion, heat resistance,resistance against sticking under heat and bonding properties, and whichis free from elution of a plasticizer and generates no toxic gas whenincinerated.

The multi-layered tube of the present invention can be used as it is orcan be used as a component of medical devices such as a blood tube, ablood bag, an medical solution bag, an infusion tube, a blood circuit, acatheter, etc., and particularly for a circuit for extracorporealcirculation. Further, it is not limited to medical applications, but canbe applied to various fields such as industrial fields and fields ofgeneral household articles.

1. A tube consisting of an inner, intermediate and outer resin layer,wherein the inner and outer layers are made of resin (II) and theintermediate layer is formed of resin (I), wherein resin (I) comprises:(a) 5 to 40 mass % of a polypropylene resin and (b) 95 to 60 mass % ofat least one hydrogenated copolymer selected from the group consistingof: (i) a first hydrogenated block copolymer comprising a hydrogenatedblock copolymer formed of (A) a polymer block from a vinyl aromaticcompound and (B) an isoprene polymer block, and the isoprene polymerblock (B) having a 1,2-bond and 3,4-bond content of 10 to 75 mol %, (ii)a second hydrogenated block copolymer comprising a hydrogenated blockcopolymer formed of said (A) polymer block from a vinyl aromaticcompound and (C) a polymer block from isoprene and butadiene, and thepolymer block (C) having a 1,2-bond and a 3,4-bond content of 20 to 85mol %, (iii) a third hydrogenated block copolymer comprising ahydrogenated block copolymer formed of said (A) polymer block from avinyl aromatic compound and a butadiene polymer block, and the polymerblock (D) having a 1,2-bond content of at least 30 mol %, and resin (II)comprises: (a′) 45 to 100 mass % of a polypropylene resin and (b′) 55 to0 mass % of the above at least one hydrogenated copolymer, wherein resin(II), which forms the outer layer contains 45 to 70 mass % of thepolypropylene resin and 55 to 30 mass % of the at least one hydrogenatedcopolymer, wherein resins (I) and (II) do not contain random copolymer,wherein said tube has (i) a tube/tube a shear peel strength of less than35 N, as measured on a stuck or adhered portion of the outermost layerof one said tube against the outermost layer of another said tube afterautoclave sterilization at 121° C. for 20 minutes, and has (ii) atube/film 180° peel strength of less than 10 N, as measured on a stuckor adhered portion of the outermost layer of said tube and an innermostpolypropylene layer of a sterilization bag, by the test method definedin JIS K6854 after autoclave sterilization at 121° C. for 20 minutes,wherein said resin (I) forms a thick substrate layer and resin (II)forms a connection layer thinner than the substrate layer, theconnection layer being capable of connecting to another tube or articleby hot melt bonding, solvent bonding or adhesive bonding, wherein saidtube can form an arc having a radius of 20 mm without kinking, therebythe tube showing good resistance against tube/tube sticking andtube/film sticking after high-pressure steam sterilization.
 2. The tubeof claim 1, wherein said resin (II), which forms the inner layer,contains 70 to 100 mass % of the polypropylene resin and 30 to 0 mass %of the at least one hydrogenated copolymer.
 3. The tube of claim 1,wherein the tube has an outer layer/intermediate layer/inner layerthickness ratio of 20–30/940–960/20∝30.
 4. The tube of claim 1, whereinsaid first hydrogenated block copolymer has a vinyl aromatic compoundcomponent content of 10 to 40 mass %, and at least 70% of carbon—carbondouble bonds of the isoprene polymer block (B) of the first blockcopolymer are hydrogenated.
 5. The tube of claim 1, wherein said secondhydrogenated block copolymer has a vinyl aromatic compound componentcontent of 10 to 40 mass %, the polymer block (C) has an isoprenecomponent/butadiene component weight ratio of 5/95 to 95/5 and at least70% of carbon—carbon double bonds of the polymer block (C) of the secondblock copolymer are hydrogenated.
 6. The tube of claim 1, wherein saidthird hydrogenated block copolymer has a vinyl aromatic compoundcomponent content of 10 to 40 mass %, and at least 70% of carbon—carbondouble bonds of the butadiene polymer block (D) of the third blockcopolymer are hydrogenated.
 7. The tube of claim 1, wherein thehydrogenated copolymer of resin (I) is a first hydrogenated blockcopolymer obtained by hydrogenating a block copolymer formed of said (A)polymer block from a vinyl aromatic compound and said (B) isoprenepolymer block.
 8. The tube of claim 1, wherein the hydrogenatedcopolymer of resin (I) is a second hydrogenated block copolymer obtainedby hydrogenating a block copolymer formed of said (A) polymer block froma vinyl aromatic compound and said (C) polymer block from isoprene andbutadiene.
 9. The tube of claim 1, wherein the hydrogenated copolymer ofresin (I) is a third hydrogenated block copolymer obtained byhydrogenating a block copolymer formed of said (A) polymer block from avinyl aromatic compound and said (D) butadiene polymer block.
 10. Thetube of claim 1, wherein the hydrogenated copolymer of resin (II) is afirst hydrogenated block copolymer obtained by hydrogenating a blockcopolymer formed of said (A) polymer block from a vinyl aromaticcompound and said (B) isoprene polymer block.
 11. The tube of claim 1,wherein the hydrogenated copolymer of resin (II) is a secondhydrogenated block copolymer obtained by hydrogenating a block copolymerformed of said (A) polymer block from a vinyl aromatic compound and (C)a polymer block from isoprene and butadiene.
 12. The tube of claim 1,wherein the hydrogenated copolymer of resin (II) is a third hydrogenatedblock copolymer obtained by hydrogenating a block copolymer formed ofsaid (A) polymer block from a vinyl aromatic compound and said (D)butadiene polymer block.
 13. The tube of claim 1, wherein said vinylaromatic compound is styrene.
 14. The tube of claim 1, wherein thepolypropylene resin in resin (I) has a bending flexural modulus of 200to 400 MPa and the polypropylene resin in resin (II) has a flexuralmodulus of 500 to 900 MPa.
 15. The tube of claim 1 that has beensterilized.
 16. A medical device comprising the tube of claim 1connected to at least one other member.
 17. The medical device of claim16, wherein said one other member is selected from the group consistingof a blood tube, an infusion tube, a catheter, and a balloon catheter.18. A circuit for extracorporeal circulation comprising the tube ofclaim 1.